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LibJS: Ensure enlarged ArrayBuffers are filled with zeros

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Otherwise, the newly allocated bytes are uninitialized, causing UB when
reading from the buffer immediately after an enlarging resize.
This commit is contained in:
Timothy Flynn 2023-12-27 08:41:22 -05:00 • committed by Andreas Kling
parent cabd599c8b
commit 916cb256de
2 changed files with 35 additions and 1 deletions
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34
Userland/Libraries/LibJS/Tests/builtins/ArrayBuffer/ArrayBuffer.prototype.resize.js
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@ -54,4 +54,38 @@ describe("normal behavior", () => {
expect(buffer.byteLength).toBe(i);
}
});
test("enlarged buffers filled with zeros", () => {
let buffer = new ArrayBuffer(5, { maxByteLength: 10 });
const readBuffer = () => {
let array = new Uint8Array(buffer, 0, buffer.byteLength / Uint8Array.BYTES_PER_ELEMENT);
let values = [];
for (let value of array) {
values.push(Number(value));
}
return values;
};
const writeBuffer = values => {
let array = new Uint8Array(buffer, 0, buffer.byteLength / Uint8Array.BYTES_PER_ELEMENT);
array.set(values);
};
expect(readBuffer()).toEqual([0, 0, 0, 0, 0]);
writeBuffer([1, 2, 3, 4, 5]);
expect(readBuffer()).toEqual([1, 2, 3, 4, 5]);
buffer.resize(8);
expect(readBuffer()).toEqual([1, 2, 3, 4, 5, 0, 0, 0]);
writeBuffer([1, 2, 3, 4, 5, 6, 7, 8]);
expect(readBuffer()).toEqual([1, 2, 3, 4, 5, 6, 7, 8]);
buffer.resize(10);
expect(readBuffer()).toEqual([1, 2, 3, 4, 5, 6, 7, 8, 0, 0]);
});
});